Fossil fuels are one of the world's leading sources of energy. However, known oil reserves are finite; therefore, there exists a need to improve the process for converting crude oil into usable petroleum products.
The rising demand for oil and oil products has led to the conversion of higher molecular weight crude oils into these desired products. One method of accomplishing this conversion is by reducing the molecular weight of these heavy crude oils. One principal method utilized in reducing the molecular weight of hydrocarbons is referred to as "catalytic cracking". Generally, with this method, hydrocarbon feedstocks containing higher molecular weight hydrocarbons have their molecular weight reduced (i.e. "cracked") by being contacted under elevated temperatures with a cracking catalyst thereby producing light distillates such as gasoline.
In the catalytic cracking of hydrocarbon feedstocks, particularly heavy feedstocks, metal such as nickel, iron, copper and/or cobalt, present in the feedstocks, become deposited on the cracking catalyst promoting excessive hydrogen and coke formations. Since the production of hydrogen and/or coke generally has an adverse effect on the production of usable products, these are undesirable products of a cracking process. Although the cracking catalyst does undergo a regeneration process, the metal contaminants, which cause the excessive formation of hydrogen and coke, are not removed by a catalyst regeneration operation. Therefore, there exists a need to mitigate the adverse effects of contaminating metals on cracking catalysts.
One method of mitigating a portion of these adverse effects is through a process called metals passivation. As used hereinafter, the term "passivation" is defined as a method for decreasing the detrimental catalytic effects of metal contaminants. In accordance with such a metals passivation process, the terms "metal contaminants and/or contaminating metals" as used herein, refers to metals selected from the group consistng essentually of nickel, iron, copper and cobalt which become deposited on the cracking catalyst during a catalytic cracking process. Therefore, by passivating the contaminating metals on cracking catalysts, the catalysts' life and desired product yields can be prolonged and increased respectively.
It is known that some of the aforementioned metal deposits, which contaminate cracking catalysts, can be passivated by contacting the contaminated catalyst with various metals passivating compounds. One particular type of metals passivating compound is a solid passivating agent suspended in a liquid medium. There are, however, inherent problems associated with such a compound. The first problem concerns the stability of the suspended compound. Specifically, in the past, it was difficult to arrive at a composition which would maintain the solid particles suspended for a long period of time. This low degree of stability causes many problems. For example, one such problem is variations in concentrations of the suspended passivating agent. Thus, it becomes very difficult to determine the amount of passivating agent actually being discharged into the catalytic cracking unit. Moreover, another problem resulting from poor stability is that of creating a requirement to continually agitate the aqueous suspention. However, even when continually agitated, the particles of passivating agent begin to settle the instant that agitation ceases; thus, reverting to the first problem of varying concentrations of passivating agent being suspended in the aqueous solution. Therefore, one object of this invention is to provide novel compositions of suspended passivating agents which have an improved degree of stability.
Another inherent problem associated with conventional aqueous suspensions of metals passivating agents concerns the viscosity of the suspended solution. In the past, it has been difficult to arrive at a composition which is stable and effective and also maintains a low viscosity. In commercial applications a passivating agent suspended in solution which has a high viscosity often causes many problems. These problems arise since an aqueous passivating agent generally must be pumped through various conduits and ultimately dispersed into a catalytic cracking system at a relatively high velocity. When the aqueous passivating agent is viscous, commercial applications become often very difficult and sometimes even impossible. Moreover, the need for a low viscosity aqueous suspension becomes greater as the geographical ambient temperature decreases. For example, in refineries where the ambient temperature nears 0.degree. C., a solution having a low viscosity is desired. Therefore, another object of this invention is to provide a novel process for making novel compositions of suspended passivating agents which are stable and have a low viscosity.
A conventional method of carrying out the metals passivation process is by dispersing the selected metals passivating agent either directly into the hydrocarbon cracking reactor or into the hdyrocarbon feedstream. While these methods have been successful, there is always a need for new and improved metals passivation processes. Therefore, another object of this invention is to provide an improved metals passivation process resulting in a more efficient method of introducing any suitable passivating agent into or onto a contaminated catalyst so as to improve the degree of metals passivation.